1. Technical Field
This application relates to a catheter and more particularly to a multi-lumen catheter which facilitates hemodialysis.
2. Background of Related Art
Hemodialysis is a well known method of providing renal (kidney) function by circulating blood. The kidneys are organs which function to extract water and urea, mineral salts, toxins, and other waste products from the blood with filtering units called nephrons. From the nephrons the collected waste is sent to the bladder for excretion. For patients having one or both defective kidneys, the hemodialysis procedure is life saving because it provides a machine to simulate the function of the kidneys.
In the hemodialysis procedure, blood is withdrawn from the patient's body through a catheter or tube and transported to a dialysis machine, also commonly referred to as a kidney machine. The catheter is typically inserted through the jugular vein and maneuvered into position through the superior vena cava into the right atrium to provide high blood flow. In the dialysis machine, toxins and other waste products diffuse through a semi-permeable membrane into a dialysis fluid closely matching the chemical composition of the blood. The filtered blood, i.e. with the waste products removed, is then returned to the patient's body. In some instances, the catheter may be left in place for several years. As can be appreciated, proper access to the patient's blood and transport of the blood to and from the dialysis machine for this extended period of time is critical to hemodialysis.
One example of a dialysis catheter currently being marketed is the MedComp Ash Split catheter. This catheter has two lumens, one for arterial flow and the other for venous flow, which are each D-shaped in cross-sectional configuration. The catheter is bifurcated at its distal end to separate the lumens and the catheter is manually split to the desired length for selected separation before insertion into the target area. Another well-known catheter is a Med Comp catheter which has the venous flow lumen terminating proximally, i.e. axially recessed, from the arterial flow lumen. Each of these lumens is also D-shaped in cross-sectional configuration.
The use of a tear away sheath in catheter insertion is well known. It would be advantageous if a dialysis catheter could be provided which would also provide for readily insertion without the use of a tear away sheath in certain instances. Such insertion method, if utilized, can decrease the complexity of the procedure.
Another area of dialysis catheter design is to maximize venous and arterial flow rates while preventing collapsing the lumens. That is, it is known that the larger lumens will maximize flow rates, reduce arterial and venous pressure and improve dialysis by providing fastener dialysis. However, given the limited amount of space in the dialysis catheter, which is typically about 15-16 French, the size of the lumens is limited. The size is also limited by the fact that if the lumens are too large, the wall thickness of the catheter becomes too thin, thereby reducing the strength of the wall and resulting in collapse of the lumens which has a detrimental affect on the blood flow.
In navigating vessels to access the target site, such as the right atrium, it is desirable to provide the smallest catheter profile, i.e. the smallest outer diameter catheter body. This profile facilitates insertion through smaller vessels as it reduces the likelihood of the catheter engaging the wall of the vessel and reduces trauma to the vessel by minimizing frictional contact with the vessel wall. However, the desire for smaller diameter catheters must be balanced against the need for providing sufficient sized lumens to enable proper blood flow. If the lumens are too small, sufficient blood flow may not be able to be maintained and the blood can be damaged during transport. Also, a sufficient relationship must be maintained between the size of the lumens and the overall diameter of the catheter to maintain the structural integrity of the catheter.
Numerous attempts have been made in the prior art to optimize the multi-lumen configuration. In some approaches, such as disclosed in U.S. Pat. Nos. 4,568,329 and 5,053,023, the inflow and outflow lumen are provided side by side in D-shaped form. In other approaches, such as those disclosed in U.S. Pat. Nos. 4,493,696, 5,167,623 and 5,380,276 the inflow and outflow tubes are placed in concentric relation. Other examples of different lumen configurations are disclosed in U.S. Pat. Nos. 5,221,256, 5,364,344, and 5,451,206. Commonly assigned U.S. Pat. Nos. 6,814,718 and 7,011,645 disclose other lumen configurations.
The catheter lumen configuration must accommodate two competing factors: keeping the catheter as small as possible to facilitate insertion while keeping the lumens as large as possible for blood flow. This balance must be achieved while maintaining the structural integrity of the catheter. It would therefore be advantageous to provide a catheter which reaches an optimum compromise between these two competing factors.
Another important feature of dialysis catheters is the suction openings to withdraw blood. Keeping the suction openings clear of thrombolytic material and away from the vessel wall is clearly essential to dialysis function since an adequate supply of blood must be removed from the patient to be dialyzed.
The need therefore exists for an improved dialysis catheter which facilitates the surgical dialysis procedure, reduces unwanted kinking of the catheter during insertion and use, and strikes an optimal balance between overall catheter size and lumen size.